A transmissometer may be described as, but without limitation, an instrument for measuring the extinction coefficient of the atmosphere and for the determination of visual range. A tranmissometer typically operates by sending a narrow, collimated beam of energy (usually a laser) through a propagation medium. A narrow field of view receiver at the designated measurement distance determines how much energy is arriving at the detector, and determines the path transmission and/or extinction coefficient. Transmissometers may be referred to, but without limitation, as telephotometers, transmittance meters, or hazemeters.
Currently there is no commercial apparatus available to provide real time spatial dust density distribution in a large volume. Point sampling transmissometers are sometimes used; however, the spatial samplings from these types of transmissometers are finite and typically limited by beam and detector size. Additionally, the spatial resolution provided by point sampling transmissometers is limited.